The kinetics of the immune response to experimental cholera have been studied in the chinchilla. A significant increase (fourfold rise) in antivibrio rosette forming cells (RFC) was observed in Peyer's patches and lamina propria as early as the second day with peak levels occurring about the fifth day. A similar increase in spleen and mesenteric lymph nodes was not observed earlier than the third or fourth day with peak levels occurring about the tenth daa. Significant increases (fourfold rise) in antitoxin RFC appeared earlier in Peyer's patches and lamina propria; however, these increases were not observed until the fifth day post inoculaiton at which time the antivibrio RFC responses had already reached peak levels. Although appearance of antivibrio plaque forming cells (PFC) was somewhat variable, significant increases in Peyer's patches and lamina propria were observed about the third day. These responses in antivirbrio PFC are compativle with the anitvibrio RFC responses in Peyer's patches and lamina propria and with the increases in intestinal IgA and IgG during the acute stage of cholera in the chinchilla. Anitvibrio PFC were predominately of the IgA class. Serum IgA and IgG remained essentially unchanged during the acute and early convalescent stages of the disease. During convalenscence both serum IgA and IgG increased 20% above control levels. Intestinal IgA and IgG increased sharply during the first 2 days of infection but decreased to levels below control levels between the second and fourth day. Thereafter IgG increased to 80% above the control by the seventh day, and IgA to 50% by the fifteenth day. The ratio of IgA/IgG ranged from 3.0/1.0 to 2.0/1.0. IgA and IgG in serum and intestinal secretions decreased to approximately 20% of control levels by the thirteenth day. These studies appear consistent with the notion that immune response to cholera does occur locally, at least during the early stages of the disease, rather than in lymphoid tissues remote from the site of antigenic stimulation. We hope that our studies will provide useful information which can be used to better define that immune system operating in cholera, the nature of the protective antibody functioning in the gut, and the relationdship between intestinal antibody and progress of infection in experimental cholera. The informatio (Text Truncated - Exceeds Capacity)